With the rapid development of display technologies, touch panels (touch screen panels) have already spread all over people's lives. At present, touch panels can be classified into an add-on mode touch panel, an on-cell touch panel and an in-cell touch panel according to formed structures. For the add-on mode touch panel, a touch panel and a liquid crystal display (LCD) are produced separately, and then are attached together to form a liquid crystal display panel having a touch function. The add-on mode touch panel has disadvantages such as a higher production cost, a lower light transmittance and a thicker module. For an in-cell touch panel, touch electrodes of a touch panel are embedded inside a liquid crystal display panel, so that the overall thickness of the module can be thinned, and the production cost of the touch panel can be reduced greatly as well, and thus it becomes attractive to the major panel manufacturers.
At present, a capacitive in-cell touch panel is implemented by adding touch driving electrodes and touch sensing electrodes to a TFT (thin film transistor) array substrate directly and additionally. That is, two layers of strip-like ITO electrodes that are non-uniplanar and intersect each other are produced on a surface of the TFT array substrate, and these two layers of ITO (Indium Tin Oxides) electrodes act as touch driving electrodes and touch sensing electrodes of the touch panel, respectively. As illustrated in FIG. 1, a mutual capacitance Cm is produced between a touch driving electrode Tx that is transversely arranged and a touch sensing electrode Rx that is longitudinally arranged. When a finger touches the panel, value of the mutual capacitance Cm can be changed by the touch of the finger, and a touch detection device detects the position of a touch point of the finger by detecting the variation of the currents respectively corresponding to the capacitances Cm before and after the finger's touch.
Two kinds of mutual capacitances Cm can be formed between a touch driving electrode Tx that is transversely arranged and a touch sensing electrode Rx that is longitudinally arranged. As shown in FIG. 1, one is the projective capacitance that is effective for achieving a touch function (curves with arrowheads in FIG. 1 denote the projective capacitance), and when a finger touches the panel, the value of the projective capacitance can be changed; and the other one is the facing capacitance that is unuseful for achieving a touch function (straight lines with arrowheads denote the facing capacitance), and when a finger touches the panel, the value of the facing capacitance can not be changed.